CN1189939C - Semiconductor device and its making method - Google Patents

Abstract

A semiconductor device comprises a semiconductor substrate, a plurality of bump electrodes formed on the semiconductor substrate, and a sealing film, formed on the semiconductor substrate of the between the bump electrodes,having a top surface located higher than a top surface of each bump electrode and an opening for exposing the top surface of each bump electrode.

Description

Semiconductor device and manufacturing method thereof

technical field

The present invention relates to a semiconductor device in which a plurality of bump electrodes are formed on one surface of a semiconductor substrate composed of silicon or the like and a sealing film is formed between the bump electrodes. A semiconductor device having a structure in which the surface of the film is low and the stress acting on bonding elements formed on bump electrodes is relieved, and a method for manufacturing the same.

Background technique

A semiconductor device including the above stress relaxation structure is called a CSP (chip size package), and is shown in FIG. 8 as an example. In this semiconductor device, a structure is formed in which connection pads 2 are formed on the surface of a semiconductor substrate 1 made of silicon or the like, an insulating film 3 is formed on the surface except for the central portion of the connection pads 2, and from The rewiring 5 is formed on the surface of the connection pad 2 exposed through the opening 4 formed on the insulating film 3 to a predetermined place on the surface of the insulating film 3, and a bump electrode 6 is formed on the surface of the pad part at the front end of the rewiring 5. On the entire surface except the bump electrode 6, the sealing film 7 is formed so that the surface thereof is higher than the surface of the bump electrode 6, and the bump electrode 6 is formed in the opening 8 formed on the sealing film 7 and on its upper side. Solder balls 9 for electrical connection.

In this case, the surface of the bump electrode 6 is lowered than the surface of the sealing film 7, and the solder ball 9 electrically connected to the bump electrode 6 is formed in the opening 8 formed on the sealing film 7 and on the upper side thereof. After the semiconductor device is packaged on a circuit substrate (not shown), when performing a temperature cycle test, etc., it is not easy to cause stress due to the difference in thermal expansion coefficient between the semiconductor substrate 1 and the circuit substrate. Cracks are generated at the interface between the bump electrodes 6 and the solder balls 9 .

Next, an example of the method for manufacturing the semiconductor device will be described with reference to FIGS. 9 to 12 in order. First, as shown in FIG. 9, the connection pad 2 is formed on the surface of the semiconductor substrate 1 in a wafer state, and the insulating film 3 is formed on the part except the central part of the connection pad 2 on the surface. Rewiring 5 is formed on the surface of connection pad 2 exposed from opening 4 formed on 3 to a predetermined position on the surface of insulating film 3, and on the surface of pad portion at the front end of rewiring 5, as an example, a bump with a height of about 120 μm is formed. Point electrode 6.

Next, as shown in FIG. 10 , on the entire surface of the insulating film 3 including the bump electrodes 6 and the rewiring 5 , a layer having a thickness smaller than that of the bump electrodes 6 is formed by a transfer method, a dispensing method, a dipping method, a printing method, or the like. A sealing film 7 made of slightly thick epoxy resin. Therefore, in this state, the surface of bump electrode 6 is covered with sealing film 7 .

Next, as shown in FIG. 11, by grinding the surface side of the sealing film 7 and the surface side of the bump electrode 6, the surface of the bump electrode 6 is exposed, and the exposed surface of the bump electrode 6 is bonded to the sealing film. The surface of 7 is the same plane. In this case, the polishing not only exposes the surface of the bump electrode 6 but also processes the surface of the sealing film 7 , so the surface side of the bump electrode 6 is polished to about 30 μm. Therefore, the height of bump electrode 6 in this state is about 90 μm.

Next, as shown in FIG. 12 , the surface side of the bump electrode 6 is etched by about 30 μm by a half-etching process to form an opening 8 in the sealing film 7 . Therefore, the height of bump electrode 6 in this state is about 60 μm. Next, as shown in FIG. 8 , solder balls 9 electrically connected to the bump electrodes 6 are formed in the openings 8 formed in the sealing film 7 and on the upper sides thereof. Next, after a dicing process, a semiconductor device composed of individual chips is obtained.

However, in the above-mentioned conventional semiconductor device, the initial height of the bump electrode 6 is about 120 μm, which is relatively high, and after the grinding treatment and half-etching treatment combined with surface processing, the height of the bump electrode 6 is reduced to the initial height. Half of that, about 60 μm, reduces the relaxation of the stress on the bump electrode 6 itself. Here, there is a method of further increasing the initial height of the bump electrode 6, but the resist film when the bump electrode 6 is formed by electroplating becomes thicker, and the light transmittance in the thickness direction when coating and exposing the semiconductor substrate is reduced. It is difficult to be uniform, and there is a limit to formation by photolithography. Even assuming that the problems of resist film formation and exposure are overcome, the method of etching about 60 μm after forming a high bump electrode by plating is obviously low in productivity. Furthermore, the height of the bump electrode 6 varies due to the half-etching process, and further the height of the solder ball 9 varies, so that connection failure with the circuit board occurs.

Contents of the invention

An object of the present invention is to efficiently increase and make the height of the bump electrode uniform in a semiconductor device having a bump electrode including a stress relaxation structure.

According to the present invention, there is provided a semiconductor device in which a sealing film is formed thicker than the height of the bump electrodes, and openings exposing the upper surfaces of the respective bump electrodes are formed in the sealing film.

According to this configuration, since the upper surface of the bump electrode is located at a position lower than the upper surface of the sealing film, it has a function of relieving stress acting on the interface of the adhesive formed on the bump electrode. Since the openings of the sealing film can be formed without performing an etching process that increases the variation in the height of the bump electrodes, the height of the bump electrodes can be made uniform and efficient production can be performed.

Description of drawings

1 is an enlarged sectional view showing a semiconductor device according to Embodiment 1 of the present invention;

2 is an enlarged cross-sectional view illustrating an initial manufacturing process of the manufacturing method of the semiconductor device shown in FIG. 1;

Fig. 3 is an enlarged cross-sectional view illustrating a process continued from Fig. 2;

Fig. 4 is an enlarged cross-sectional view illustrating a process continued from Fig. 3;

Fig. 5 is an enlarged cross-sectional view illustrating a process continued from Fig. 4;

6 is an enlarged cross-sectional view showing a semiconductor device according to a modified example of the first embodiment;

7 is an enlarged cross-sectional view of a semiconductor device according to a second embodiment of the present invention;

FIG. 8 is an enlarged cross-sectional view of a conventional semiconductor device;

FIG. 9 is an enlarged cross-sectional view illustrating an initial manufacturing process of the manufacturing method of the semiconductor device shown in FIG. 6;

Fig. 10 is a cross-sectional view illustrating the manufacturing process following Fig. 7;

FIG. 11 is a cross-sectional view illustrating the manufacturing process following FIG. 8; and

FIG. 12 is a cross-sectional view illustrating a manufacturing process following FIG. 9 .

Detailed ways

first embodiment

FIG. 1 is an enlarged cross-sectional view showing an embodiment of a semiconductor device of the present invention, and the structure of the semiconductor device will be described below.

Connection pads 12 are formed on the upper surface of a semiconductor substrate 11 made of silicon or the like, and an insulating film 13 is formed on the upper surface of the semiconductor substrate except for the central portion of the connection pads 12 . Openings 14 exposing the connection pads 12 are formed on the insulating film 13 , and rewiring lines 15 are extended on the insulating film 13 through the openings 14 from the upper surfaces of the connection pads 12 . The rewiring 15 is formed of, for example, copper or the like. Columnar bump electrodes 16 made of copper, for example, are formed on the surface of the pad portion at the tip of each rewiring 15 . The first sealing film 17 is formed on the entire surface of the semiconductor substrate 11 exposed from the columnar bump electrodes 16 . The upper surface of the first sealing film 17 is formed substantially on the same plane as the upper surface of the bump electrode 16 . On the first sealing film 17, the second sealing film 18 having the opening 19 exposing the upper surface of each bump electrode 16 is formed. Solder balls 20 (low-melting-point metal layers) electrically connected to the bump electrodes 16 are formed in and above the openings 19 formed in the second sealing film 18 .

In this case, the upper surface of the bump electrode 16 is flush with the upper surface of the first sealing film 17, and the opening 19 formed on the second sealing film 18 formed on the first sealing film 17 and the On the upper side, the reason for forming the solder balls 20 electrically connected to the bump electrodes 16 is that after the semiconductor device is packaged on a circuit substrate (not shown), it is not easy to be damaged by the semiconductor substrate during a temperature cycle test or the like. The stress generated by the difference in thermal expansion coefficient between the bottom 11 and the circuit substrate causes cracks at the interface between the bump electrodes 16 and the solder balls 20 .

Next, an example of the method for manufacturing the semiconductor device will be described with reference to FIGS. 2 to 5 in sequence. First, as shown in FIG. 2, a connection pad 12 composed of an aluminum-based metal or the like is formed on the upper surface of a semiconductor substrate 11 in a wafer state, and a connection pad 12 is formed on a portion other than the central portion of the connection pad 12 on the upper surface. The insulating film 13 forms the rewiring 15 from the upper surface of the connection pad 12 exposed through the opening 14 formed on the insulating film 13 to a predetermined position on the upper surface of the insulating film 13, and forms the rewiring 15 on the pad portion at the front end of the rewiring 15. On the surface, as an example, columnar bump electrodes 16 having a height of about 120 μm are prepared. The formation of the bump electrodes 16 is carried out by photolithography. For example, on the entire surface of the insulating film 13, a metal film for rewiring is formed by sputtering or the like, and a photosensitive layer is formed on the metal film. A resist film is used to form openings for forming bumps on the photoresist film, and the metal film formed on the insulating film 13 is plated as one electrode to form bump electrodes 16 . After the bump electrodes are formed, the photoresist is peeled off, and the metal film is patterned by a photolithography technique to form the rewiring 15, and the state shown in FIG. 2 is obtained.

Next, as shown in FIG. 3, on the entire upper surface of the insulating film 13 including the bump electrode 16 and the rewiring 15, the bump electrode 16 having a thickness ratio of 16 is formed by a transfer method, a dispensing method, a dipping method, a printing method, or the like. The first sealing film 17 made of epoxy resin with a slightly thicker height. Therefore, in this state, the upper surface of bump electrode 16 is covered with first sealing film 17 .

Next, as shown in FIG. 4, by polishing the upper surface side of the first sealing film 17 and the surface side of the bump electrode 16, the surface of the bump electrode 16 is exposed, and the upper surface of the exposed bump electrode 16 is polished. The surface is on the same plane as the upper surface of the sealing film 7 . Since the polishing at this time does not need to finish the surface (upper surface) of the first sealing film 17 due to the formation of the second sealing film 18 described later, it is only necessary to expose the surface of the bump electrode 16 and make the exposed bump The upper surface of the point electrode 16 and the upper surface of the sealing film 7 may be flush with each other. Therefore, the upper surface side of the bump electrode 16 is polished less than conventionally (about 30 μm), for example, about 5 to 20 μm. Therefore, the height of bump electrode 16 in this state is about 100 to 115 μm.

Next, as shown in FIG. 5, on the surface of the first sealing film 17 other than the bump electrodes 16, a ring with a thickness of 10 to 15 μm, preferably 20 to 30 μm is formed by screen printing, photolithography, or the like. The second sealing film 18 made of oxygen-based resin. In this state, an opening 19 is formed in a portion of the second sealing film 18 corresponding to the upper surface of the bump electrode 16 . Next, as shown in FIG. 1 , solder balls 20 electrically connected to the bump electrodes 16 are formed inside and above the opening 19 where the second sealing film 18 is formed. Solder balls 20 may be directly mounted on each bump electrode 16 , or a reflow method of coating solder paste on each bump electrode 16 may be used. Solder paste melted by reflow forms a spherical shape due to surface tension. Then, after a dicing process, a semiconductor device composed of individual chips can be obtained.

In the semiconductor device obtained in this way, on the first sealing film 17 whose upper surface is flush with the upper surface of the bump electrode 16 by grinding, the upper surface of the bump electrode 16 is placed at a position corresponding to the upper surface of the bump electrode 16. Since the second sealing film 18 is formed with the opening 19, after the upper surface of the bump electrode 16 can be lower than the upper surface of the second sealing film 18, the height of the bump electrode 16 and the thickness of the first sealing film 17 Likewise, therefore, the height of the bump electrodes 16 can be increased and made uniform.

That is, in the above-mentioned embodiment, with respect to the initial height of about 120 μm of the bump electrode 16, since the final height is about 100 to 115 μm, it is slightly lower than the initial height, which is comparable to the conventional final height of about 60 μm. ratio can be greatly improved. As a result, relaxation of the stress generated in bump electrode 16 itself can be enhanced. Since the height of the bump electrodes 16 can be made uniform, the height of the solder balls 20 can also be made uniform, and there is no obstacle to the electrical connection with the circuit board.

By grinding the upper surface side of the first sealing film 17, the upper surface of the bump electrode 16 is on the same plane as the upper surface of the first sealing film 17. The second sealing film 18 is formed with the opening 19 at the position corresponding to the upper surface, so instead of the conventional semi-etching process, the second sealing film 18 may be formed by screen printing, photolithography, etc. Make the manufacturing process easy.

6 is an enlarged cross-sectional view showing a modified example of the semiconductor device shown in FIG. 1 . In this modified example, the size (planar size) of the opening 19 formed in the second sealing film 18 is formed slightly larger than the size (planar size) of the bump electrode 16. Therefore, the entirety of the solder ball 20 can also reliably contact the bump electrode. In order to reduce the internal stress of the solder ball 20 formed in the opening 19, the side surface of the opening 19 may be formed in an inclined shape that expands upward. In the case of FIG. 6, the size of the opening 19 formed in the second sealing film 18 is larger than that of the bump electrode 16, and its side surface is inclined upwardly, but the side surface of the opening 19 is the same as in the case of FIG. , can also be roughly vertical. In addition, similarly to FIG. 1 , the size of the opening 19 may be substantially the same as that of the bump electrode 16 , and the side surface thereof may be inclined upwardly. The openings 19 may be formed by irradiating laser light after forming the second sealing film 18 in a complete shape on the first sealing film 17 and the bump electrodes 16 .

(second embodiment)

Fig. 7 is an enlarged cross-sectional view showing a semiconductor device according to a second embodiment of the present invention. The difference between this embodiment and the first embodiment is that the sealing film 21 is one layer. The upper surface of the bump electrode 16 is located lower than the upper surface of the sealing film 21 of this one layer. Next, a method of manufacturing the semiconductor device of the second embodiment will be described. The bump electrode 16 is formed as follows: a photoresist film is formed on the upper surface of the semiconductor substrate 11 having the connection pad 12, the insulating film 13, and the wiring 15, and the photoresist film is formed by photolithography. Openings are formed at the positions of the bump electrodes 16 (photoresist is not shown), and then the bump electrodes 16 are formed by electroplating or the like, and then the bump electrodes are formed after removing the photoresist film. The upper surface of the bump electrode 16 is ground to make the height of each bump electrode 16 uniform, and then, a sealing film 21 having a film thickness thicker than the bump electrode 16 is formed by a transfer method, a dispensing method, a dipping method, a printing method, etc. (thus, The thickness of the sealing film in this case is the thickness obtained by adding the thickness of the first sealing film 17 and the thickness of the second sealing film 18 in FIGS. After polishing and planarizing the upper surface of the sealing film, a laser beam is irradiated to form openings 19 exposing bump electrodes 16 . Subsequent steps are the same as those of the first embodiment. As shown in FIG. 6, in the case of the second embodiment, the size (planar size) of the opening 19 may be larger than that of the bump electrode 16, and the side surface may be formed in an inclined shape expanding upward.

In each of the above-mentioned embodiments, a low-melting-point metal layer having approximately the same thickness may be formed by electroplating, sputtering, printing, etc., instead of the solder balls 20 of the bump electrodes 16 . Such solder balls or low-melting-point metal layers may also be formed on the connection terminals of the circuit substrate on which the semiconductor device is mounted, instead of being formed on the semiconductor device. In the above-mentioned embodiment, on the first sealing film 17, after forming the second sealing film 18 with the opening 19 on the portion corresponding to the upper surface of the bump electrode 16, immediately inside and on the opening 19 Solder ball 20 is formed on the side of bump electrode 19, but in the case where the surface of bump electrode 19 is oxidized, wet etching or dry etching may be performed to remove the oxide film on the upper surface of bump electrode 19, and after performing The solder balls 20 are formed after a metal layer formation process such as nickel plating to prevent the generation of an oxide film. The metal layer forming process is, for example, nickel plating. When the oxide film removal process is performed, the height of the bump electrode 16 is slightly lowered, but the same effect that the first sealing film is substantially on the same plane can be obtained. The size (planar size) of the opening 19 of the second sealing film 18 may be slightly smaller than the shape of the upper surface of the bump electrode 16 . In the above-mentioned embodiments, the solder balls 20 may not be formed, but may be replaced by an anisotropic conductive adhesive for electrical connection with the connection terminals of the circuit substrate.

As described above, according to the present invention, since the upper surface of the bump electrode is located lower than the upper surface of the sealing film, it has a function of alleviating stress acting on the interface of the adhesive formed on the bump electrode. In addition, since the opening of the sealing film can be formed without performing an etching process that increases the variation in the height of the bump electrodes, the height of the bump electrodes can be made uniform and can be produced efficiently.

Claims (9)

1. semiconductor device is characterized in that comprising:

Semiconductor substrate (11);

A plurality of bump electrodes (16) are formed on the described Semiconductor substrate (11);

The 1st diaphragm seal (17) is formed on the described Semiconductor substrate (11) between described bump electrode (16), and the upper surface of upper surface and described bump electrode (16) is same surface; And

The 2nd diaphragm seal (18) is formed on described the 1st diaphragm seal (17), on the position corresponding with the upper surface of described bump electrode (16) peristome (19) is arranged.

2. semiconductor device as claimed in claim 1 is characterized in that, forms low-melting-point metal layer (20) with its upside in the peristome (19) of described the 2nd diaphragm seal (18).

3. semiconductor device as claimed in claim 2 is characterized in that, described low-melting-point metal layer (20) is a solder ball.

4. semiconductor device as claimed in claim 1 is characterized in that, the planar dimension of the peristome (19) of described the 2nd diaphragm seal (18) is bigger than the planar dimension of described bump electrode (16).

5. semiconductor device as claimed in claim 1 is characterized in that, the side of the peristome (19) of described the 2nd diaphragm seal (18) forms the tilted shape that enlarges upward.

6. the manufacture method of a semiconductor device, it is characterized in that, go up formation bump electrode (16) in Semiconductor substrate (11), comprising on the described Semiconductor substrate (11) of described bump electrode (16), form the 1st diaphragm seal (17), by the upper surface side of described the 1st diaphragm seal (17) and the upper surface side of described bump electrode (16) are ground, the upper surface of described bump electrode (16) is exposed, and making the upper surface of this bump electrode that exposes (16) and the upper surface of described the 1st diaphragm seal (17) is same plane, go up formation the 2nd diaphragm seal (18) at described the 1st diaphragm seal (17), make it on the position corresponding, peristome (19) be arranged with the upper surface of described bump electrode (16).

7. the manufacture method of semiconductor device as claimed in claim 6 is characterized in that, the upper surface side of described bump electrode (16) is ground 5～20 μ m.

8. the manufacture method of semiconductor device as claimed in claim 6 is characterized in that, forms described the 2nd diaphragm seal (18) by silk screen print method or photoetching process.

9. the manufacture method of semiconductor device as claimed in claim 6 is characterized in that, forms low-melting-point metal layer (20) with its upside in the peristome (19) of described the 2nd diaphragm seal (18).

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